Generally speaking, an electromagnet used in a magnet type medical instrument which can kill a pain in a human body by means of a magnetic field generated in it comprises a core and a coil constituted by a metallic wire wound round the core and generates a magnetic field by applying an alternating current or a pulsating current to the coil.
The core of an electromagnet 30 used in a conventional magnet type medical instrument shown in FIG. 4 is constituted by sheets of silicon steel piled up so as to be shaped like a bar for example. As for this conventional type medical instrument, as soon as an alternating current is applied to the coil on condition that the electromagnet is put horizontally and magnetic powder 32 is put near a magnetic pole 31 of the core on a paper put horizontally, the powder distant from the magnetic pole is scattered rapidly while the powder near the magnetic pole is not so scattered as shown in FIG. 4. This means that the lines of magnetic force distant from the magnetic pole are scattered while those near the magnetic pole is not so scattered and that the magnetic flux density distant from the magnetic pole is low while that near the magnet pole is high. In case an alternating current was applied to the coil of the electromagnet 30 of the conventional type medical instrument on condition that the alternating voltage was 30V and the frequency was 50 Hz, the magnetic flux density 6 cm distant from a magnetic pole 31 of the core was 5% supposing the magnetic flux density at the magnetic pole 31 was 100%. Thus in this conventional type there is a problem that its pain-killing effect in a human body is small.
Thus, an object of the present invention is to propose an electromagnet and a coil for a magnet type medical instrument the pain-killing effect of which is large enough as it can keep high magnetic flux density even at any point distant from the magnetic pole of the core.
There is another problem in this conventional type that in case the electromagnet 30 shown in FIG. 4 generates a magnetic field in a human body the magnetic flux density is not constant at any part of the human body because the distance from the magnetic pole is not constant resulting in low magnetic flux density at parts distant from the magnetic pole.
Thus, another object of the present invention is to propose a magnet type medical instrument which can generate a magnetic field having a relatively uniform magnetic flux density in a human body.
There is furthermore another problem in this conventional type that in case the electromagnet 30 generates a magnetic field in a human body only an alternating current of 50 or 60 Hz in frequency is used to excite the coil for the electromagnet 30 although it is known that the effect of a frequency other than 50 or 60 Hz is better.
Thus, another object of the present invention is to propose a magnet type medical instrument in which an alternating current in an optimum frequency range can excite the coil for the electromagnet 30 in the medical instrument.